Seal ring structures are commonly used to surround integrated circuit devices, image sensor devices including front and back-illuminated image sensor devices, and other semiconductor devices formed on a silicon or other semiconductor chip. The seal ring structures internally or externally surround the silicon or other semiconductor chip that includes the semiconductor device to isolate the semiconductor device and protect it from stress energy from other components. Stress energy in components external to the semiconductor chip could propagate to and destroy the semiconductor device on the semiconductor chip if not for the presence of the seal rings.
One example of a seal ring structure is a trench that extends around the periphery of the chip and another example is a trench that extends around the periphery of the semiconductor chip but is filled with a material different than the substrate material which is typically silicon or other suitable materials.
Semiconductor chips are manufactured on semiconductor substrates and have a rectangular shape. This rectangular shape enables the individual chips to be separated by dicing along straight lines in orthogonal directions. The dicing takes place along scribe lines between the chips. Because semiconductor chips are rectangular in shape and because seal rings extend around the semiconductor chips, seal rings are also rectangular in shape. At the corners of these rectangularly shaped seal rings are orthogonal corners. These right angle corners are susceptible to stress and charge concentration due to their shape and structure. The stress and charge concentration can cause the seal ring structure to fracture at such corners when exposed to stress and charge concentration. Any fracturing or voiding in the seal ring provides a path for external stresses and charges to reach the semiconductor chip itself. This can result in device destruction.
It would be desirable to provide seal ring structures that are immune to stress effects and localized charge concentration build up.